In Carboniferous and Permian Epochs 153 



of different strata, unless the observer has himself dug out 

 the fossils and noted the exact locations and relations. He 

 tabulates eleven distinct marine bands. And in regard 

 to these, as compared with the greatly more extensive and 

 thick terrestrial bands, Hind in a palaeontolo^ical Supple- 

 ment says that there are two distinct molluscan faunas, 

 which recur with irregular alternations. The freshwater 

 fauna is characterized by the Unio-like genera Carhonicola 

 and Anthracomya, and the Dreissensia-like Naiadites; the 

 other by Pterinopecten papyraceus, Possidonella, with many 

 species of cephalopods, and the two never mix. 



But on the succeeding page he states, for "the marine 

 band associated with the Gin-mine Coal" that the two 

 elasmobranch genera Listracanthus and Edestiis occur in 

 it. Quoting other localities for Listracanthus he reaches the 

 conclusion that "Listracanthus is associated with a marine 

 fauna. We may therefore consider that Listracanthus 

 always had a marine habitat. Many of the fishes associated 

 with it in the bed below the Gin-mine are also found with 

 a non-marine fauna," and he appends a list setting this 

 forth. Bolton (70^:424) and Woodward (70^:486) also 

 record Listracanthus in nodules of shale strata, and con- 

 clude that these are all marine beds. So it evidently is an 

 elasmobranch which had largely left a freshwater habitat 

 and mainly lived in marine surroundings. This is discussed 

 later (p. 275). But here it may be said that all of the 

 other fishes listed by Hind (p. 529), and including Edestus, 

 were freshwater. 



The environal relations of Coal-measure organisms 

 have been so often described, and more or less correctly 

 figured, that a general word-picture is unnecessary. Nor, 

 in view of the surprising similarity of the rocks, of the 

 factors which gave rise to these, and of the organisms 

 enclosed, need we deal with localized areas, in their physical 

 or biological relation to fishes. Rather it might at once 

 be stated — in view of the knowledge we now have of Coal 

 Measure strata and their fossils — that some such compact 

 and yet extensive connecting land areas, as are traced by 

 Freeh (705:83) are a necessity for the understanding 

 of the facts and problems involved. 



